Many orthodontic treatment techniques move teeth in a procedure involving two stages. In the initial stage the forces applied to the crowns of the teeth displace the crown more than the root causing a tipping movement. The latter stage utilizes moments of force which are also applied to the crowns of the teeth in order to upright the roots and place them in a position of proper axial inclination, commensurate with normal function, favorable aesthetics, and stability. This latter stage may be termed the torquing stage.
Lingual root torque is difficult to achieve particularly on the maxillary anterior teeth. One reason for this is that all forces must be applied to the crown, while the center of resistance to moving the roots is located in a remote position along the apical portion of the root surface. This results in a situation of severe mechanical disadvantage.
There are several orthodontic appliances that have been directed at root torquing. Many of the early approaches generally consisted of three basic elements: 1) metal bands which circumferentially encompass the crown of each tooth and are attached to each tooth by cementation; 2) brackets of varying configurations affixed to the metal bands; and 3) base arch wire—usually of a U-shape which fits through slots in each of the brackets. The base arch wire is generally round or rectangular in cross-section. In some applications brackets have been attached directly to the tooth surface by means of bonding. The arch wire may act in an active or passive capacity. In the passive mode, it may act as a track along which the teeth are repositioned. Alternatively, the active mode incorporates deformations into the base arch wire during fabrication of the wire. When an orthodontic professional places the arch wire into position within the bracket slots, these deformations may serve to produce forces and moments which move teeth during orthodontic treatment.
Other attempts at orthodontic torquing have been made using a loop and a pair of legs on substantially the same plane. In this type of approach, each leg terminates in a pair of coil sets, each of the coil sets are helically wound and the outer coil set is closely associated with and fixedly anchored to the arch wire while the other coil-set of each pair is maintained free of the arch wire and in unrestricted movement with respect to the arch wire. The loop engages the labial surface of a tooth and applies force to the tooth.
These past approaches, however, have been ineffective for their purpose. For example, attaching coil sets to an arch wire in the past has involved soldering, slide fitting, and/or force fitting. None of these approaches have exhibited commercial viability and thus the long-felt need to provide orthodontic torquing has gone unmet. Generally, orthodontic professionals cannot solder the coil sets to an arch wire because material limitations cause the coil sets to immediately degrade and crumble when soldered. Similarly, efforts to crimp the coils to an arch wire result in broken coils. Force and/or slide fitting can no longer be practical because modern arch wires do not exhibit the square edges of old wires.
Thus, it is desired to provide an orthodontic torquing system that does not have the ineffectiveness of the above described systems.